The effects of hormones on cyclic nucleotide-dependent protein kinases in intact mammalian tissues will be investigated. The substrate specificities and other physical and kinetic properties of the protein kinases will be studied. Possible evolutionary relationshps of the protein kinases and their isozymes will be explored. Detailed studies of cyclic nucleotide binding and subunit interactions will be performed. The role of phosphorylation reactions in the effects of insulin and other hormones on "low Km" phosphodiesterase will be investigated.